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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 211 · 40 sums
TalentJR

The method (Inside 180, outside the sum): Angle sum: ∠A + ∠B + ∠C = 180°. Exterior angle = sum of the two interior opposite angles. Right-angled triangle: longest side² = side² + side² (3, 4, 5 and 5, 12, 13 are famous sets). Sides can make a triangle only if the two shorter sides add up to more than the longest side.

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  1. 1.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  2. 2.Can a triangle have sides of 4 cm, 4 cm and 8 cm? (a) No (b) Yes
  3. 3.In an isosceles triangle, the angle between the two equal sides is 106°. What is each of the other two angles (in degrees)?
  4. 4.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  5. 5.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  6. 6.In triangle ABC, angle A = 100° and angle B = 21°. What is angle C (in degrees)?
  7. 7.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 49° and 53°. What is the exterior angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  10. 10.An exterior angle of a triangle is 82°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 79° and 29°. What is the exterior angle (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 34° and 39°. What is the exterior angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  15. 15.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  16. 16.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 52° and 36°. What is the exterior angle (in degrees)?
  20. 20.Can a triangle have sides of 4 cm, 14 cm and 8 cm? (a) No (b) Yes
  21. 21.The two interior opposite angles of a triangle are 58° and 76°. What is the exterior angle (in degrees)?
  22. 22.Can a triangle have sides of 9 cm, 4 cm and 9 cm? (a) Yes (b) No
  23. 23.In an isosceles triangle, the angle between the two equal sides is 110°. What is each of the other two angles (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  25. 25.In triangle ABC, angle A = 78° and angle B = 24°. What is angle C (in degrees)?
  26. 26.In triangle ABC, angle A = 97° and angle B = 37°. What is angle C (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  30. 30.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  34. 34.Can a triangle have sides of 10 cm, 6 cm and 9 cm? (a) No (b) Yes
  35. 35.In an isosceles triangle, the two equal angles are 64° each. What is the third angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  39. 39.In triangle ABC, angle A = 75° and angle B = 26°. What is angle C (in degrees)?
  40. 40.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?

Answer key

  1. 17
  2. No
  3. 37
  4. 15
  5. 48
  6. 59
  7. 20
  8. 102
  9. 36
  10. 26
  11. 64
  12. 108
  13. 73
  14. 100
  15. 17
  16. 59
  17. 21
  18. 33
  19. 88
  20. No
  21. 134
  22. Yes
  23. 35
  24. 78
  25. 78
  26. 46
  27. 20
  28. 84
  29. 73
  30. 24
  31. 61
  32. 116
  33. 75
  34. Yes
  35. 52
  36. 40
  37. 65
  38. 45
  39. 79
  40. 8

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